a region of southeast China containing Hong Kong Island as well as many other islands and the adjacent mainland. Hong Kong was a British colony from the 1840s until 1997 when it was reverted to Chinese rule as a "Special Administrative Region." While it is a part of China and controlled by the Chinese government on all matters related to defense and foreign affairs, Hong Kong operates with a great deal of autonomy, with its own legal system, police force, immigration policy, and currency.